The present invention relates generally to servo methods and apparatus for use in disk drives, and more particularly, to methods and apparatus for reducing seek acoustics in disk drives.
Disk storage devices generally include a plurality of data disks which rotate at a preselected speed via spindle motor, and an actuator for moving a head carrier that supports transducers (read/write heads), across the rotating disks to write data to or read data from concentric data tracks on the disks. The actuator moves the transducers in a substantially radial direction across the rotating disks in response to an input signal which controls supply of an electrical current to a motor in the actuator for governing the movement of the actuator, and therefore the transducers, towards destination tracks. The actuator may cause the transducer to accelerate, decelerate, or move at a constant velocity. The actuator current is arranged to generate torque that causes the actuator to rotate to a desired position for the actuator as required by a seek command.
To access a destination track, in a seek operation a transducer is moved radially across the tracks from a starting track to the destination track. Thereafter, the rotation of the disk moves a target block of the destination track under the transducer where data is written to or read from. The amount of time required for accessing that target block, or access time, includes the time spent for the seek operation in positioning a transducer over the destination track, settling time, and a rotational latency which is the time for the segment on the destination track to rotate under the transducer.
Decreasing the access time increases the disk data throughput. In order to reduce access time, conventional disk drives utilize a velocity profile for controlling application of seek currents to the actuator to rapidly move the transducer across the disk to minimize access time. Typically, the transducer is moved between data tracks by supplying seek currents to the actuator to initially accelerate the transducer from the starting track up to a maximum target velocity and then decelerate the transducer to the destination track.
However, the transition from acceleration to deceleration in conventional disk drives is generally defined by a sudden change in the polarity of the actuator current from full power in one direction (e.g. positive) to full power in an opposite direction (e.g. negative). This rapid change in current exerts rapidly changing forces on the actuator, causing vibration of the actuator and the disk drive, and resulting in acoustical noise. The acoustical noise is highly undesirable. To reduce the vibrations and acoustical noise, in conventional disk drives a predetermined transducer radial velocity profile is stored in memory, wherein the velocity profile defines programmed actuator current levels for the seek operation to reduce acoustic noise for random seeks.
A disadvantage of such conventional disk drives is that the velocity profile is designed to minimize access time for random seeks in computer systems. This is particularly problematic where conventional disk drives are utilized for storage of Audio Visual/Video (AV) content in AV systems, such as in consumer electronics (e.g., Digital Video Recorders or DVRs). This is because certain AV disk drive access patterns (e.g. dual streaming due to simultaneous record and playback from the same disk) require non-random seeks that generate significantly higher acoustic noise than random seeks in computer systems. As such, conventional disk drives utilizing techniques for achieving acoustic noise reduction as measured for random seeks, do not meet the acoustic requirements of AV systems.
There is, therefore, a need for method and apparatus for reducing acoustical noise induced during seek operations in disk drives utilized for storage of AV content. There is also a need for such method and apparatus to reduce acoustic noise without throughput degradation for the disk drive. There is also a need for such method and apparatus to allow the use of the disk drive in AV applications as well as in computer.
The present invention satisfies these needs. In one embodiment the present invention provides a method for performing seek operations in a disk drive including at least one data disk having multiple concentric data tracks thereon, and a transducer radially moveable relative to the data tracks by an actuator during a seek operation from a starting track to a destination track. Upon receiving a request for a seek, a seek profile is utilized to control application of current to the actuator based on the seek profile, wherein the seek profile includes actuator current control values, and can include transducer target velocity control values for the seek operation based on the starting and destination tracks, to achieve a desirable acoustic output. Actuator current is applied to the actuator motor as a function of the control values to perform the seek operation at or below the desired acoustic output.
In one embodiment, determining the seek profile includes the steps of: for a seek operation from a starting track to a destination track, determining an empirical actuator current control value that provides a desirable acoustic output from the disk drive in response to controlled application of current to the actuator motor as a function of the current control value; relating the current control value to the seek operation based on the seek length and location, wherein the seek length represents the distance between the starting and destination tracks, and the seek location represents the radial locations of the starting and destination tracks; and storing the current control value in a memory device, and thereafter, using the current control value to perform seek operations in the disk drive.
Determining the seek profile can further include the steps of: determining an empirical actuator/transducer target velocity control value that provides a desirable acoustic output for the disk drive in response to controlled application of current to the actuator motor as a function of the target velocity control value; relating the target velocity control value to the seek operation based on the seek length and location; and storing the target velocity control value in a memory device, and thereafter, using the current and target velocity control values to perform seek operations in the disk drive.
In another aspect, the present invention provides a disk drive apparatus comprising: at least one data disk having multiple concentric data tracks thereon; an actuator including an actuator motor; a transducer radially moveable relative to the data tracks by the actuator; a servo system including a seek profile, for generating actuator current commands to perform at least one seek operation from a starting track to a destination track, the seek profile including actuator current level and transducer target velocity control values for the seek operation in relation to the starting and destination tracks, to achieve a desirable acoustic output in response to controlled application of actuator input current to the actuator motor as function of the control values; and a driver coupled to the servo system and the actuator motor, wherein the driver is arranged to receive at least one current command value to generate an input current waveform to the actuator motor. The disk drive can be a component of an AV system.